This invention relates to an impingement tube received within a turbine component, and in which the impingement tube has an inner and outer portion, with the outer portion being configured to minimize dirt blockage of impingement air at the leading edge. In one embodiment, the inner and outer portions are formed as separate pieces, and in another embodiment, the inner and outer portions are formed as a single piece.
Turbine engines have a number of components. One type of component is a stationary vane. The vanes are in the path of hot air downstream of a combustor, and have a leading edge that faces the hot air. The vane is thus exposed to high temperatures and requires cooling. One method utilized to cool the vane, is to form the vane to have hollow areas, and place impingement tubes within the hollow areas. The impingement tubes have a number of holes for directing impingement air outwardly to points within the vane. Holes also extend through the wall of the vane in order to direct the impingement air onto an outer surface of the vane.
This application relates to an impingement tube used within the hollow area of the vane that receives cooling air from both inner and outer vane cooling air supplies. One known way of supplying impingement cooling air from both inner and outer supplies is to use an impingement tube which includes an outer portion and an inner portion. Each of the inner and outer portions have an end wall roughly at an intermediate position within the vane, and with end walls both being generally parallel to an axis of rotation for the turbine. Outer cooling air is brought within the outer portion and inner cooling air is brought within the inner portion. The holes within the impingement tube portions and the vane are concentrated adjacent the leading edge of the vane.
It has been found that the air from a radially outer source carries more dirt than air from a radially inner source. The holes in the impingement tube and vane are relatively small, and are sometimes clogged by dirt within the impingement airflow. When this dirt clogs the holes near the leading edge, less air than may be desirable is directed to the leading edge.